1. Field of the Invention
The present invention relates to a semiconductor device and a method of fabricating the same, and more particularly, it relates to a semiconductor device having an interlayer dielectric film and a method of fabricating the same.
2. Description of the Prior Art
In recent years, wires must be refined and multi-layered in order to further increase the degree of integration of a semiconductor integrated circuit. In order to multi-layer the wires, an interlayer dielectric film is provided between the wires. If the surface of the interlayer dielectric film is not flat, steps result in the wires formed on the interlayer dielectric film. Thus, the wires may disadvantageously be disconnected.
Therefore, the surface of the interlayer dielectric film (i.e., the surface of a device) must be rendered as flat as possible. The technique of flattening the surface of the device, referred to as planarization, is increasingly becoming important following refinement and multi-layering of the wires in recent years. An organic SOG (spin on glass) film is known as an interlayer dielectric film frequently employed in planarization. In particular, planarization utilizing flowability of an interlayer dielectric film material is actively developed in recent years.
In order to form the organic SOG film, a solution prepared by dissolving a silicon compound in an organic solvent is dripped on a substrate while rotating the substrate. Thus, a coating of the solution is formed thickly on concave portions of steps defined on the substrate by wires and thinly on convex portions thereof, to relax the steps. Consequently, the surface of the coating of the solution is flattened.
FIGS. 26 and 27 are schematic sectional views for illustrating a process of forming multilevel interconnections of a conventional semiconductor device. A conventional method of forming multilevel interconnections with an interlayer dielectric film of an organic SOG film is now described with reference to FIGS. 26 and 27. First, lower wires 101 are first formed, followed by deposition of a silicon oxide film 106a, an organic SOG film 104 and a silicon oxide film 106b, as shown in FIG. 26. The silicon oxide film 106b is flattened by CMP (chemical mechanical polishing).
Then, contact holes 107 reaching the upper surfaces of the lower wires 101 are formed in the silicon oxide film 106a, the organic SOG film 104 and the silicon oxide film 106b by general photolithography and anisotropic etching, as shown in FIG. 27. A metal material such as tungsten (W), copper (Cu) or aluminum (Al) is formed in the contact holes 107 and on the silicon oxide film 106b and part of the metal material located on the silicon oxide film 106b is thereafter removed by CMP or etch back, thereby forming contact plugs 103b. Thus, multilevel interconnections having excellent flatness can be formed by employing the organic SOG film 104 as part of an interlayer dielectric film.
When employing the organic SOG film 104 as the interlayer dielectric film, however, the contact plugs 103b are disadvantageously oxidized or corroded due to moisture and hydroxyl groups discharged from the organic SOG film 104. Consequently, the electric characteristics of the contact plugs 103b are disadvantageously deteriorated.
Further, the organic SOG film 104 discharges gas of moisture etc. into the contact holes 107 when forming the contact plugs 103b, to increase the pressures in the contact holes 107. Thus, flowability of the contact plugs 103b is deteriorated to disadvantageously result in defective embedding of the contact plug 103b. Consequently, the electric characteristics of the contact plugs 103b are disadvantageously reduced.
An object of the present invention is to provide a semiconductor device capable of preventing a contact plug (conductive member) embedded in an interlayer dielectric film from oxidation and corrosion and keeping the electric characteristics of the conductive member excellent.
Another object of the present invention is to provide a method of fabricating a semiconductor device without discharging gas of moisture etc. into a contact hole (opening) when embedding a conductive member in an interlayer dielectric film.
A semiconductor device according to an aspect of the present invention comprises an interlayer dielectric film, a conductive member embedded in the interlayer dielectric film and a side wall insulator film formed on the side surface of the conductive member.
In the semiconductor device according to the aforementioned aspect, the side wall insulator film formed on the side surface of the conductive member inhibits moisture and hydroxyl groups contained in the interlayer dielectric film from reaching the conductive member. Thus, the conductive member can be prevented from inconvenience such as oxidation or corrosion resulting from moisture and hydroxyl groups discharged from the interlayer dielectric film. Consequently, the electric characteristics of a contact part can be kept excellent.
In the semiconductor device according to the aforementioned aspect, the side wall insulator film preferably contains a material having a function of intercepting moisture and hydroxyl groups. Thus, the side wall insulator film can readily intercept moisture and hydroxyl groups.
In this case, the side wall insulator film preferably includes at least either a silicon oxide film or a silicon nitride film. In this case, further, the silicon oxide film preferably includes a silicon oxide film containing phosphorus and boron added thereto. Thus, the process time for forming the side wall insulator film can be reduced due to the high etching rate of the silicon oxide film containing phosphorus and boron added thereto. Further, the amount of the upper surface of the conductive member as scraped can be reduced due to reduction of the process time for forming the side wall insulator film.
In the semiconductor device according to the aforementioned aspect, the interlayer dielectric film preferably includes an SOG film. Thus, the interlayer dielectric film can be formed with excellent flatness.
In the semiconductor device according to the aforementioned aspect, the interlayer dielectric film preferably includes a coating film containing at least 1 mass % of carbon. When the interlayer dielectric film contains carbon, the mechanical strength of the interlayer dielectric film can be improved. Further, the dielectric constant of the interlayer dielectric film can be reduced. Consequently, parasitic capacitance between multiple wiring layers arranged through the interlayer dielectric film can be reduced.
In the semiconductor device according to the aforementioned aspect, an impurity is preferably introduced into the surface of the interlayer dielectric film. Thus, the portion of the interlayer dielectric film containing the introduced impurity is further improved in mechanical strength, to be capable of preventing a wafer crack resulting from a crack of the interlayer dielectric film caused in a step of polishing the interlayer dielectric film. Further, the portion of the interlayer dielectric film containing the introduced impurity is improved in wettability, to be capable of preventing the surface of the interlayer dielectric film from scratches caused in the step of polishing the interlayer dielectric film.
In the semiconductor device according to the aforementioned aspect, the interlayer dielectric film is preferably formed between a first conductive layer and a second conductive layer, and the first conductive layer and the second conductive layer are preferably electrically connected with each other through the conductive member embedded in the interlayer dielectric film. In this case, the second conductive layer may be formed on the upper surface of the interlayer dielectric film to be in contact with the conductive member. Further, the interlayer dielectric film may include a wiring groove formed on the upper portion of the conductive member, and the second conductive layer may be embedded in the wring groove to be in contact with the conductive member.
A method of fabricating a semiconductor device according to another aspect of the present invention comprises steps of forming a dummy interlayer dielectric film on a first conductive layer, forming an opening in the dummy interlayer dielectric film, forming a conductive member in the opening, etching back the dummy interlayer dielectric film, forming an interlayer dielectric film to cover the conductive member and forming a second conductive layer on the interlayer dielectric film to be in contact with the conductive member.
In the method of fabricating a semiconductor device according to the aforementioned aspect, the conductive member is formed with the dummy interlayer dielectric film before forming the interlayer dielectric film, to require neither a step of performing etching for forming an opening in the interlayer dielectric film nor a step of charging and embedding the conductive member in the opening of the interlayer dielectric film. Consequently, the electric characteristics of a contact part can be improved also when preparing the interlayer dielectric film from a material hard to etch or a material discharging a large quantity of moisture etc. in formation of the conductive member.
In the method of fabricating a semiconductor device according to the aforementioned aspect, the dummy interlayer dielectric film preferably includes a silicon oxide film containing phosphorus and boron added thereto. Thus, the process time for forming the side wall insulator film can be reduced due to the high etching rate of the silicon oxide film containing phosphorus and boron added thereto. Further, the amount of the upper surface of the conductive member as scraped can be reduced due to reduction of the process time for forming the side wall insulator film.
In the method of fabricating a semiconductor device according to the aforementioned aspect, the dummy interlayer dielectric film preferably contains a material having a function of intercepting moisture and hydroxyl groups. Thus, the side wall insulator formed by etching back the dummy interlayer dielectric film can readily intercept moisture and hydroxyl groups. In this case, the dummy interlayer dielectric film preferably includes at least either a silicon oxide film or a silicon nitride film.
In the method of fabricating a semiconductor device according to the aforementioned aspect, the step of forming the interlayer dielectric film preferably includes a step of forming the interlayer dielectric film by rotational coating. Thus, the conductive member can be completely embedded without causing voids (cavities).
In the method of fabricating a semiconductor device according to the aforementioned aspect, the step of etching back the dummy interlayer dielectric film preferably includes a step of forming a side wall insulator film on the side surface of the conductive member by etching back the dummy interlayer dielectric film. In this case, the side wall insulator film can inhibit moisture and hydroxyl groups contained in the interlayer dielectric film from reaching the conductive member. Thus, the conductive member can be prevented from inconvenience such as oxidation or corrosion resulting from moisture and hydroxyl groups discharged from the interlayer dielectric film. Consequently, the electric characteristics of a contact part can be kept excellent.
The method of fabricating a semiconductor device according to the aforementioned aspect preferably further comprises a step of ion-implanting an impurity into the interlayer dielectric film. Thus, the portion of the interlayer dielectric film containing the introduced impurity is further improved in mechanical strength, to be capable of preventing a wafer crack resulting from a crack of the interlayer dielectric film caused in a step of polishing the interlayer dielectric film. Further, the portion of the interlayer dielectric film containing the introduced impurity is improved in wettability, to be capable of preventing the surface of the interlayer dielectric film from scratches caused in the step of polishing the interlayer dielectric film.
A method of fabricating a semiconductor device according to still another aspect of the present invention comprises steps of forming a dummy interlayer dielectric film on a first conductive layer, forming an opening in the dummy interlayer dielectric film, forming a conductive member in the opening, etching back the dummy interlayer dielectric film, forming an interlayer dielectric film to cover the conductive member, forming a wiring groove reaching the conductive member in the interlayer dielectric film and embedding a second conductive layer in the wiring groove to be in contact with the conductive member.
In the method of fabricating a semiconductor device according to the aforementioned aspect, the conductive member is formed with the dummy interlayer dielectric film before forming the interlayer dielectric film, to require neither a step of performing etching for forming an opening in the interlayer dielectric film nor a step of charging and embedding the conductive member in the opening of the interlayer dielectric film. Consequently, the electric characteristics of a contact part can be improved also when preparing the interlayer dielectric film from a material discharging a large quantity of gas of moisture etc. in formation of the conductive member.
In the method of fabricating a semiconductor device according to the aforementioned aspect, the dummy interlayer dielectric film preferably includes a silicon oxide film containing phosphorus and boron added thereto. Thus, the process time for forming the side wall insulator film can be reduced due to the high etching rate of the silicon oxide film containing phosphorus and boron added thereto. Further, the amount of the upper surface of the conductive member as scraped can be reduced due to reduction of the process time for forming the side wall insulator film.
In the method of fabricating a semiconductor device according to the aforementioned aspect, the dummy interlayer dielectric film preferably contains a material having a function of intercepting moisture and hydroxyl groups. Thus, moisture and hydroxyl groups can be readily intercepted. In this case, the dummy interlayer dielectric film preferably includes at least either a silicon oxide film or a silicon nitride film.
In the method of fabricating a semiconductor device according to the aforementioned aspect, the step of embedding the second conductive layer in the wiring groove preferably includes a step of depositing the second conductive layer to be embedded in the wiring groove and thereafter removing an excessive deposited portion by polishing. Thus, the method includes no step of etching the second conductive layer, whereby the second conductive layer can be prepared from a material hard to etch.
In the method of fabricating a semiconductor device according to the aforementioned aspect, the step of forming the interlayer dielectric film preferably includes a step of forming the interlayer dielectric film by rotational coating. Thus, the conductive member can be completely embedded without causing voids (cavities)
In the method of fabricating a semiconductor device according to the aforementioned aspect, the step of etching back the dummy interlayer dielectric film preferably includes a step of forming a side wall insulator film on the side surface of the conductive member by etching back the dummy interlayer dielectric film. In this case, the side wall insulator film can prevent moisture and hydroxyl groups contained in the interlayer dielectric film from reaching the conductive member. Thus, the conductive member can be prevented from inconvenience such as oxidation or corrosion resulting from moisture and hydroxyl groups discharged from the interlayer dielectric film. Consequently, the electric characteristics of a contact part can be kept excellent.
The method of fabricating a semiconductor device according to the aforementioned aspect preferably further comprises a step of ion-implanting an impurity into the interlayer dielectric film. Thus, the portion of the interlayer dielectric film containing the introduced impurity is further improved in mechanical strength, to be capable of preventing a wafer crack resulting from a crack of the interlayer dielectric film caused in a step of polishing the interlayer dielectric film. Further, the portion of the interlayer dielectric film containing the introduced impurity is improved in wettability, to be capable of preventing the surface of the interlayer dielectric film from scratches caused in the step of polishing the interlayer dielectric film.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.